1. Field of the Invention
The present invention relates to polygalactomannan compositions and more particularly derivatized guar gum compositions which, when dispersed in water, are capable of forming a relatively transparent solution. The compositions are particularly useful for applications where clarity and purity of aqueous solutions are desirable such as oil recovery, personal care products, textile chemicals, paper chemicals, paints, and the like.
2. Technology Description
Natural and synthetic polymers containing hydroxy groups have been used as thickeners for foods, coatings, paints, explosive slurries, oil well fluids, cosmetics and other personal care products, and many other functional applications.
One class of polymers that have been widely used as suspending and viscosity agents are polygalactomannans. Polygalactomannans are polysaccharides composed principally of galactose and mannose units and are usually found in the endosperm of leguminous seeds such as guar, locust bean, honey locust, flame tree, and the like. The polygalactomannans may be used in either their natural form or may be substituted with one or more functional groups (e.g., carboxymethyl group). The most commonly used polygalactomannan is guar gum. In practice, to thicken a fluid the polygalactomannans may either be added by themselves, or with other viscosity modifiers such as other polysaccharides, xanthan gum and the like.
While the use of polygalactomannans, and guar gum in particular, as thickening agents has been met with great success, it is still desired to improve the physical properties of the guar gum when dispersed in a solution such as water. One such property is its ability to transmit light when used as an aqueous solution. Aqueous solutions of guar gum tend to be opaque or translucent at best. It is particularly desired that clear, colorless and less impure solutions be produced when dispersing guar gum in water as it makes the final solution more useful for the above-described applications. It is believed that the presence of insolubles is largely responsible for the inability to obtain clear solutions.
U.S. Pat. No. 4,693,982 discloses the use of enzymes to reduce insolubles in guar gum. The level of clarity produced by the enzymatic treatment is not disclosed in the patent.
U.S. Pat. No. 4,874,854 discloses low viscosity heteropolysaccharides, for example, guar gum. Example 3 discloses a "clarified" guar gum which is produced by cold filtration of a 0.3% solution through diatomaceous earth and precipitated with isopropyl alcohol. The ability of this material to transmit light is not disclosed in the patent.
U.S. Pat. No. 3,912,713 discloses non-lumping derivatives of guar gum produced by derivatizing guar gum splits at a moisture content of 20-80% by weight, raising the moisture content of the splits, if necessary, to 30-80% by weight and fragmenting the splits by pressing them out in a thin layer and drying them on a cylinder heated to 100.degree.-180.degree. C. and comminuting the film to form particulates of a size in the order of +20 mesh, as measured by a Tyler screen, and preferably having a size of 2-5 mm. This process is commonly referred to as drum drying. According to Example 3, the product produced in the Example gives a "clear solution having no lumps or clots on stirring in water". No quantitative definition of "clear" (i.e. light transmittance) is presented in the patent.
U.S. Pat. No. 4,057,509 discloses polygalactomannan allyl ether gels. According to Example 1, guar gum is purified to yield a material having less than 0.1% nitrogen content and about 0.48% ash. The same purification method is described in U.S. Pat. No. 4,169,945.
U.S. Pat. No. 4,659,811 teaches the treatment of 100 parts of guar gum with at least 150 parts of an aqueous alkali solution whereby the water present in the entire solution exceeds 60%. No data regarding the ability of resulting aqueous solutions to transmit light is set forth.
Despite the above advances, it is believed that the above processes are able to produce guar gum which, when dissolved in solution at 0.5 weight percent, is able to only provide minimal light transparency, i.e., no more than 50-60% at 500-600 nm.
Accordingly, there exists a need in the art for a derivatized guar gum which is capable of producing nearly pure, clear and colorless solutions upon dispersing in water and a novel process for producing the gum.